Department of Chemical Engineering II

University of Lund, Sweden

by

Mona Axman, Carl Danielsson, Nadia ElBaba,

Emil Henriksson, Peter Möller, Patrik Persson,

Malin Wennberg,

Ingemar Bjerle, Christian Künkel and Erik Nord.

This report is a study of a new incineration procedure of hazardous medical waste in Skåne. Presently the medical waste is divided into two fractions, biological and remaining waste, which are incinerated separately. Due to the contamination risk it is desirable to combust all medical waste, consisting of biological, contaminated and cutting, together. All waste is collected in 700l-cartons in each hospital.

Two different incineration plants are compared. Plant #1 has a batch combustion procedure where the cartons are burnt whole. Plant #2 has a continuous combustion procedure where the cartons are shredded before combustion. To locate the plants three parameters are considered. These parameters are availability to natural gas and district heating as well as transport costs. Plant #1 has to be situated near an existing air polution control plant (APC) due to periodically high polution values. Optimization of above parameters results in plant #1 being situated in Malmö and plant #2 in Lund.

Both plants are designed to incinerate 2500 tons medical waste per year. Plant #1 is in use 16 hours per day and has a capacity of 7 cartons per hour. The size of the oven is approximately 10 to 12 m³. Plant #2 consists of four separate lines, each with two combustion chambers with a capacity of 600 tons per year. The size of a combustion chamber is 2.5 m in diameter and a height of 2.5 m. After combustion the gasflow passes through a heat exchanger and a quenching section before it enters the APC plant.

A newly built APC plant is only required for plant #2 and two different alternatives are compared. The first one is based on injecting activated carbon and hydrated lime after the quench and then letting the gases pass through a fabric filter. The second alternative is a packed bed scrubber which is 5 m high and with a diameter of 0.8 m which reduces the hydrocloric acid from 1000 ppm to 1 ppm. The absorption liquid must be neutralized after it leaves the scrubber.

To calculate the financial viability of each plant, an investment calculation is performed. The plants are estimated to have a financial lifespan of 25 years and after this time the value is put to zero. The calculation rate is put to 8 per cent. By using the investment calculation a minimum price for handling the waste was determined. Plant #1, situated in Malmö, has been established to have the lowest minimum price namely 11 400 SEK per ton waste. A change in capital investment of ± 10 per cent results in a minimum price variation of ± 250 SEK per ton waste. A reduction of the interest rate to 6 per cent results in a minimum price of 11 000 SEK per ton waste and to 4 per cent a minimum price of 10 500 SEK per ton.

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